Economic Scene; Controlling world population growth: where to put the money.

By Peter Passell

Published: April 21, 1994

THE world's population is expected to double by 2050, with most of the increase in countries that can ill afford to feed or educate more children. And many -- probably most -- people think they know what to do about it. The historian and futurist Paul Kennedy, for example, writes that "the only practical way to insure a decrease in fertility rates and thus population growth is to introduce cheap and reliable birth control."

In fact, the widespread view that what stands in the way of population stability is the lack of a perfect contraceptive is no longer taken seriously by researchers. Establishment demographers, including John Bongaarts of the Population Council, acknowledge that family planning can have only a "limited impact on population growth." And some economists would go further.

"Unwanted fertility," argues Lant H. Pritchett of the World Bank, "plays a minor role" in explaining why African women average twice the number of births as their Asian counterparts.

While this might at first seem a distinction without a difference, it figures prominently in the debate about how to spend scarce social development funds. And it is likely to reach center stage at next September's International Conference on Population and Development in Cairo.

Fertility rates are, indeed, strongly correlated with use of contraception, Mr. Pritchett explains in the March issue of the Population and Development Review. In East Asia, where 75 percent of married women use contraception, the average family has 2.3 children. In Africa just 17 percent use contraception and average 6.1 children.

But correlation says nothing about cause and effect. It is possible that the desire to limit children drives the use of contraceptives, or that some third factor -- family income, urbanization, the social status of women -- drives both.

This is hardly nitpicking. While modern contraception makes it easier for Kenyans to limit family size, they have not responded. And other cultures have managed sharp declines without help from science: 19th-century northern Europeans had lower fertility rates than their counterparts today in middle-income countries.

Not surprisingly, much of the modern research in family planning has focused on isolating the births that are "unwanted" and presumably linked to lack of access to birth control. Mr. Bongaarts uses survey data to calculate that one in five births in low-income countries was undesired. Hence while other factors may matter more in explaining variations in birth rates, he believes that a major push on family planning could reduce world population from the currently projected 14.6 billion in the year 2100 to a mere 10 billion.

This is not the last word on the subject, though. Using standard statistical techniques to test the link between actual births and desired family size, Mr. Pritchett found that all but 10 percent of the country-to-country variation can be explained by the demand for children alone.

Ten percent is less than 20 percent, but is still a big number. Would better access to birth control take a big bite out of these unwanted births? Mr. Pritchett thinks not, estimating that variation in the prevalence of contraception independently explains a mere 2 percent of variations in fertility.

The result defies common sense and, arguably, evidence from the one controlled experiment to bring birth control and related family health services to the poor in Bangladesh. Begun in 1977, an all-out effort in the Muslim Matlab region succeeded in reducing fertility from 6.7 to 5.1 children.

The catch, Mr. Pritchett says, is that it was incredibly expensive -- six times the average cost of family planning in Bangladesh, which already had an aggressive planning effort by third world standards. In some cases, individual women were visited 300 times by case workers.

Where does that leave the debate? Almost everyone agrees that convincing families that small is beautiful matters more than stocking the clinics with condoms and pills. By the same token, almost everyone agrees there is some payoff to making birth control cheap and easy. And David Bloom, an economist at Columbia University, notes that it is difficult to differentiate the two effects since family planning expands women's control over their destiny and thus may reduce their desired family size.

The issue now is where to put the marginal population-control dollar. Women's education might produce the higher return. This, in any event seems the democratic approach, one that contrasts with China's coercive effort to defuse the population bomb in a single generation.

But virtue may not prove its own reward. For one thing, it is far from proved that advancing women's rights will pay big dividends in reducing desired family size. For another, birth control is beginning to do double duty, slowing the spread of AIDS as well as reducing fertility.

The biggest worry, perhaps, is a rift in the coalition between those who favor women's equality on its own merits and those who have invested public money and personal reputations on the success of family planning. "It's already hard enough to get policy makers to worry about social development," Mr. Bloom lamented.